Elevator cab isolation



June 24, 1941. HYMANS 2,246,732

ELEVATOR CAB ISOLATION Filed Nov. 7, 1939 2 Shets-Sheet 1 June 24, 1941.HYMANS ELEVATOR CAB ISOLATION Filed Nov. '7, 1939 2 Sheets-Sheet 2INVENTOR ATTORNEY Patented June 24, 1941 ELEVATOR CAB ISOLATIONFrederick Hymans, Larchmont, N. Y., assignor to Otis Elevator Company,New York, N. Y., a corporation of New Jersey Application November 7,1939, Serial No. 303,194

6 Claims. (01. 187-1) The invention relates to elevators and especiallyto the suspension of the elevator cab.

In many elevator installations there are vibrations in the hoistingmechanism which are transmitted to the cab through the hoisting ropesand the'framework within which the cab is mounted. This is moreprevalent in the case of geared machines where vibrations are set up dueto the gearing itself as a result of slight inaccuracies in manufacture.Vibrations may be due to other causes, for example, those set up by theropes running over the hoisting sheave or those set up in the hoistingmotor itself. Vibrations of the latter nature are possible with gearlessas well as geared machines. Transmission of vibrations to the elevatorcab is objectionable because it is felt by the passengers. Also, if thefrequency of any of the vibrations is in the audible range, anobjecticnal hum is set up in the cab.

It is the object of the invention to provide a suspension for theelevator cab which reduces the vibrations transmitted thereto to anegligible value.

The invention involves supporting the elevator cab upon elastic meansarranged between the cab and the framework. The elastic means are sochosen that, for a cab of a given weight plus the weight of the maximumload to which the cab may be subjected, the natural frequency ofvibrations of this mass suspended by the elastic means is considerablyless than the frequency of vibrations transmitted to the framework. Thisrenders the vibrations transmitted from the framework to the cab ofnegligible value.

Features and advantages of the invention will become apparent from thefollowing description and appended claims.

In the drawings:

Figure 1 is a schematic view in perspective of an elevator cab andframework therefor, em-

bodying the invention:

Figure 2 is a plan view showing the manner in which the platform of thearrangement in Figure 1 is supported by the framework;

Figure 3 is a view in section taken along the line 33 of Figure 2;

Figure 4 is an enlarged sectional detail of the comprises an enclosureIll mounted on a platform II. The cab is arranged within a framework l2comprising the safety plank l3, uprights l4 and crosshead l5. Theuprights are in the form of channels and the safety plank and thecrcsshead comprise a pair of channels secured to the sides of theuprights. Hoisting ropes 18 are secured to the crosshead throughthumblerods A pair of angle members 20 and 2! are secured as by bolts I9 to the top of the safety plank, one at each end of the plank. Theangle members extend crosswise of the plank inside the uprights, towhich they are secured by countensunk screws 42, to angle members 43welded to the uprights. These members are of a length equal to the depthof the car and are connected at their ends by additional angiemembers 22and 23 running parallel to the safety plank. These latter angle membersare secured to plates 24 by bolts 29, plates 24 in turn being welded tomembers 20 and 2|. This forms a frame 25 for supporting the platform. Oneach side of the cab are two angle braces 25 and 21. These braces aresecured at their upper ends to the upright 14 and at their lower ends tothe angle pieces l8 welded to the ends of members 20 and 2|, apertures28 being provided in each angle piece to receive securing bolts. Thisprovides a rigid support for the frame 25, thus obviating any tendencyfor the frame to tilt. In certain installations these braces may beomitted.

The cab is supported on elastic means arranged between the cab platformand the frame 25. In

the embodiment illustrated, a plurality of rubber pads 30 are utilizedfor this purpose. Each pad is provided with a plurality of apertures 3|(see Figure 5). These apertures are illustrated as closed at their tops,for convenienceof molding, but the apertures may extend through thepads.

These pads are located one at each end of each of the angle members 20and 2|. Each pad is positioned with respect to frame 25 by means of abolt 32 secured to the angle member with its head extending upwardlyinto one of the apertures 3| in the pad. An angle member 33 is securedto the bottom of' the platform at each corner thereof to fit against theinner sides of the frequency of vibration which is considerably lessthan the frequency of the vibrations transmitted to the framework. Toprovide such a system, not only must the weight of the cab and theweight of the accessories and passengers which may be carried thereby beconsidered but also the construction and properties of the rubber padswhich determine their elasticity. The elasticity of the pads isdependent on their effective supporting area, their bulge area, and theproperties of the rubber.

For example, in one installation in which the hoisting motor drives thehoisting sheave through the intermediary of a worm gear, the fullrunning speed of the hoisting motor is 1000 R. P. M., thisbeing analternating current machine operating on 50 cycles. The motor drives thehoisting sheave through a triple thread-worm. Due to some slightimperfection in manufacture of the worm, vibrations of a frequency of3000 cycles per minute were transmitted to the sheave shaft. Thesevibrations were taken up by the hoisting ropes which in turn transmittedthem to the framework. From the framework these vibrations weretransmitted to the cab. This was effectively reduced to a negligiblevalue by providing elastic supporting means for the elevator cab inaccordance with the invention. The weight of the cab and accessoriesplus the maximum load to which it was subjected was in the neighborhoodof 3600 lbs. Six pads were provided between the car platform and thesupporting framework. Each of these pads was 6 inches long. 3% incheswide and 1 inch thick and was provided with apertures to give aneffective area of each pad of 13 square inches with a bulge area of 45square inches. Rubber of the following composition was used:non-cold-flow rubber of a tensile strength of 300 lbs. per square inchminimum, an elongation at 3000 lbs. of 600% minimum, 12% maximum coldflow at 600 lbs. per square inch, and a durometer hardness of 35 to 45.This providedanaturalfrequencyvibrationof the cab on the pads in theneighborhood of 540 vibrations per minute or about one-sixth of thefrequency of the transmitted vibrations. This natural frequency ofvibration increased as the load decreased but was still suflicientlysmall as compared with the transmitted vibrations to render the effectof the transmitted vibrations substantially negligible.

It often happens that there are present several harmonics of the mainfrequency of vibration. Elastic means which are of the proper elasticityto effectively dampen vibrations of the main frequency are alsoeffective to dampen the harmonics as their natural frequency is asmaller fraction of the harmonics than of the main frequency. Inasmuchas the framework for the cab is not a solid mass, vibrations transmittedthereto from the hoisting ropes exist in different directions. Theelastic supporting means for the cab effectively dampens all thesevibrations, those in a sidewise direction being taken up by the sheerelasticity of the supports.

Utilizing pads of the same character, isolation against the transmissionof vibrations of other frequencies or in installations of other loads onthe elastic supporting means may be effectively accomplished by varyingthe supporting area of the pads. In the construction illustrated inFigure 2 two additional pads have been illustrated, these pads beingsplit crosswise and the halves 34 positioned at intermediate pointsalong angle members 20 and 2|. These pads are kept in position by meansof bolts extending into apertures as previously described. Pads may alsobe provided on the top of the channels of the safety plank whereadditional supporting area is desired.

While rubber pads have been described as used to support the cab, it isto be understood that other elastic means may be utilized, as forexample coil springs. 'Also certain variations in construction may bemade, as well as variations in the manner in which the cab is supportedby the elastic means. The elasticity of the supporting means is chosenso that the natural frequency of vibration of the mass on the elasticmeans is a small percentage of the impressed frequency, without makingit so small as to give a feeling of insecurity to passengers in the car.

In some installations it is desirable to hold the cab in place at thetop as by a locking plate 35. Such arrangement has been illustrated.Referring to Figures 6 and 7, this plate, assuming a wood cab, issecured to the top of the cab as by screws 36. This locking plate isprovided with an opening 31 to permit the plate to straddle the upright,the opening being of a size to provide a clearance between the plate andthe face and two sides of the upright. Rubber pads 38 are providedbetween the face and sides of the upright and the plate, being held inplace respectively by clamps 40 secured to the locking plates as bybolts 4|. Rubber pads of the same character as those employed underneaththe cab may be utilized for this purpose, thereby preventing thetransmission of any vibrations or jars through the locking plate to thecab.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an elevator system in which an elevator cab is arranged within aframework suspended by a plurality of hoisting ropes, supporting memberssecured to said framework, and a plurality of rubber pads arrangedbetween said cab and said supporting members for supporting said cab outof contact with said supporting members and framework, the relationshipbetween the thickness, bulge area, total effective supporting area andcomposition of the pads being such as to provide a natural frequency ofvibration of said cab on said pads which is small as compared with thefrequency of vibrations transmitted to said framework from said hoistingropes.

2. In an elevator system in which the elevator cab is arranged withinframework suspended by hoisting ropes and in which the cab has aplatform, a supporting frame for said cab secured to said framework,elastic means arranged beneath said cab between the cab platform andsaid frame for supporting said cab, means for locating said elasticmeans with respect to said frame, and means for locating said cabplatform with respect to said elastic means and thus said cab withrespect to said frame to isolate said cab from said frame and framework.

3. In an elevator system in which the elevator cab is arranged withinframework suspended by a plurality of hoisting ropes and in which saidcab has a platform, a supporting frame for said cab secured to saidframework, a plurality of rubber pads arranged beneath said cab betweensaid platform and said frame for supporting the cab, each pad having aplurality of vertical apertures, members extending from said frame intoapertures in said pads for locating said pads on said frame, and meanssecured to said platform for locating said platform with respect to saidpads and thus said cab with respect to said frame, to isolate said cabfrom said frame and framework.

4. In an elevator system in which the elevator cab is arranged withinframework suspended by a plurality of hoisting ropes, said frameworkcomprising a pair of uprights jointed at the top and bottom, supportingmembers secured to said framework, and elastic means arranged betweensaid cab and said supporting members and between the top of the cab andsaid uprights to isolate said cab from said supporting members and saidframework, said elastic means being of an elasticity such as to reduceto a negligible value the transmission of vibrations to said cab fromsaid framework which have been transtted to said framework from saidhoisting ropes.

5. In an elevator system in which the elevator cab is arranged withinframework suspended by a plurality of hoisting ropes and in which saidframework comprises a pair of uprights joined at the top and bottom;supporting members secured to said framework; a plurality of rubber padsarranged between said cab and said supporting members for supportingsaid cab out of contact with said supporting members and framework, saidpads having a thickness, a bulge area provided by a plurality ofapertures in the pads, a total effective supporting area and com:position, the relationship between said thickness, bulge area,supporting area and composition being such that the natural frequency ofvibration of said cab on said pads is small as compared with thefrequency of vibrations trans mitted to said framework by said hoistingropes; means cooperating with said pads for locating the bottom of thecab with respect to said framework; means for locating the top of thecab with respect to said framework; and similar rubber pads arrangedbetween said top locating means and said uprights.

6. In an elevator system in which the elevator cab is arranged withinframework suspended by a plurality of hoisting ropes and in which saidcab comprises a platform and an enclosure on said platform and saidframework comprises a pair of uprights joined at the top by a crossheadand at the bottom by a safety plank; a supporting frame for saidplatform secured to said framework; members connecting the corners ofsaid frame to said uprights; a plurality of rubber pads arranged betweensaid cab and said supporting members for supporting said cab out ofcontact with said supporting members and framework, said pads having athickness, a bulge area provided by a plurality of apertures in thepads, a total effective supporting area and composition, therelationship between said thickness, bulge area, supporting area andcomposi-' tion being such that the natural frequency of vibration ofsaid cab on said pads is small as compared with the frequency ofvibrations transmitted to said framework by said hoisting ropes; meanscooperating with said pads for locating said platform with respect tosaid framework; 'a pair of locking plates secured to the top of the caband cooperating with said uprights to position the top of the cab, eachplate having an opening straddling the upright for which it is provided;similar rubber pads arranged between the sides and face of each uprightand its cooperating locking plate; and means securing said last namedpads to said locking plates.

FREDERICK HYMAN S.

